The present invention relates to a new and improved steering apparatus.
A known power steering apparatus is disclosed in U.S. Pat. No. 3,918,544. The apparatus includes a piston and cylinder type motor. A hollow piston rod is connected with one end of the piston and extends through an end wall of the motor cylinder. The head end working area of the piston exceeds the rod end working area of the piston by an amount which is equal to the cross sectional area of the piston rod.
Upon actuation of a power steering control valve in this known apparatus, fluid pressure is ported to either the rod or head end portion of the motor cylinder to effect movement of the piston. As this occurs, a screw member connected with the piston is rotated to provide feedback indicative of the extent of movement of the piston. A seal at one end of the screw member engages the inside of the hollow piston rod to form a chamber between the seal and the axially outer end portion of the piston rod. This chamber is connected with a reduced or drain pressure.
In a steering apparatus such as the one shown in U.S. Pat. No. 3,918,544, the working area of the head end of the piston exceeds the working area of the rod end of the piston by an amount which is equal to the cross sectional area of the tubular wall of the piston rod. The difference in the working areas on the head and rod ends of the piston tends to result in the application of different steering forces to the vehicle wheels during turns in opposite directions, even though the extent and rate of rotation of the vehicle's steering wheel in each direction is the same.